erp5: Add google-api-python-client that is requred for Google OAuth

stack/erp5/buildout.cfg

 [buildout]
+
 extends =
 # Exact version of Zope
   ztk-versions.cfg
@@ -565,6 +566,8 @@ eggs =
 
 # Needed for parsing .po files from our Localizer subset
   polib
+# Needed for Google OAuth
+  google-api-python-client
 
 # parameterizing the version of the generated python interpreter name by the
 # python section version causes dependency between this egg section and the
@@ -694,6 +697,7 @@ eventlet = 0.19.0
 five.formlib = 1.0.4
 five.localsitemanager = 2.0.5
 greenlet = 0.4.10
+google-api-python-client = 1.5.3
 http-parser = 0.8.3
 httplib2 = 0.9.2
 huBarcode = 1.0.0